On 06/11/2018 07:29, Jeff Liebermann wrote:
Incidentally, the owner of the MJF-259B has graciously allowed me to
use it for an experiment. I plan to replace the 10 AA cell battery
pack (15.0V) abomination with a 4 cell LiPo or LiIon battery packet
(14.8V) and an external charger. I'm also looking into a replacement
LCD display that has backlighting. I'll post the results when it's
done and hopefully working.

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Li-ion and LiPo cells are nominally 3.7 V but when fully charged 4.2 V,
hence 4 cells in series would initially give 16.8 V
Question : Would 16.8 V not be too high for the MFJ 259B ?

The above cells should NOT be discharged below 3.0 Volt in order not to
loose capacity .
It means the voltage of the pack should NOT drop below 12.0V .

I assume you intend charging the above cells outside the analyser
,otherwise you would have to include a max voltage circuit for each cell
when charging the cells in series. These circuit boards can be cheaply
bought from Chinese online retailers , but highly like there is NOT
enough space for the 4 cells + the circuit board inside the analyser
enclosure.

Good Luck with the repairs

Frank , EI7KS